Step 3: Leg Hardware
Now install the leg hardware. Put in the socket/anchor, and put a small nail through the hole so it doesn't turn. It should fit snugly, and the nail isn't really necessary. Then put the knob through the washer and feed it through the opposite side into the socket. Repeat for the other pair, and you should now have two working joints.
Finding the Hardware
The black knobs + screws that I used are very hard to find. Most places do not have these. Big chain hardware stores (lowes/home depot) carry similar 3-prong triangle knobs with screws attached, but the screws are usually not very long. For alternatives, the easiest thing to find would be a normal bolt and a wingnut. Instead of turning the knob/screw into the T nut, you turn the wingnut on the stationary bolt. Same effect, different parts.
Those stores also have wingnut/bolt combos - basically a bolt with a wingnut on the end. If you can find one long enough, these are probably the best alternative.
Optional jackfishjoe checker mod:
Thanks to an idea by Strapped-4-Cache , which was tested out by jackfishjoe , we have a great mod for the joints. Normally the joints are held in place by the friction of the wood, and the pressure of the bolts holding the wood together. This requires a lot of pressure and can be a pain sometimes. A better way to do this is to insert plastic checkers pieces so the "teeth" grab each other and prevent movement.
-drill a hold through the center of 4 checkers
-carve a circular impression/hollow in each leg for the checkers to be inset slightly. This will be on the sides facing each other, so the knob goes through each checker.
-assemble the legs like so: knob - washer - wood - checker - checker - wood - socket.
The checkers should face each other and lock into place via the teeth, and when assembled you shouldn't really be able to notice the checkers. This will allow you to use less pressure to lock the feet in place, and avoid cracking the wood (or having the platform slump down and accidentally drop you laptop).